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Segregation, raceways, tank, o verwintering pond.⇐ ПредыдущаяСтр 25 из 25
Exercise 152. Make up collocations using words from both columns.
Exercise 153. Look through the text and find information about: - the primary culture system used in the world today; - management and harvesting become difficult; - ponds can be stocked at various densities; - shapes of the tank; - pens and net enclosures are used in shallow water; - haps are very easy to manage.
Exercise 154. Translate the following sentences from Russian into English. 1. О сновной системой культуры, используемой в современном мире, является з емляной пруд. 8. С лив происходит через центр резервуара по стояку или нижнему сливу, окруженному экраном. Exercise 15 5. Test yourself by answering these questions and summarize given information. What do Earthen ponds include? What is the largest type of pond? What is the primary culture system used in the world today? What is the function of steeper slopes? What provides a proper finctioning of pods? What are r aceways. Where are culture cages and net pens used? How do the shapes of tank affect the aquaculture process? What is n et enclosure usually made from?
Under which conditions do management and harvesting become difficult?
Text C It is interesting to know Water exchange
VOCABULARY LIST TO TEXT C
Exercise 156. Translate the following sentences from English into Russian. Water exchange, offset evaporation, static pond culture, supplementary feeds, artificial circulation, incidental losses, high stocking densities, recirculation technology, aeration equipment, high capital coast, careful management, nitrogen compounds. Read the text and translate. Be ready to discuss. According to water exchange there are two main systems: Static systems Much global aquaculture production uses traditional pond culture methods. These ponds are static, with no exchange of water during the culture period. There may be some topping up to offset evaporation. Static pond culture is usually extensive because of major problems in maintaining water quality under conditions of a large biomass of cultured fish per unit volume of static water. Increasing biomass requires increasing inputs of fertilizers and supplementary feeds to maintain productivity. This, in turn, requires management for such water quality problems as unacceptable levels of nitrogen compounds and low DO levels at night. With supplementary aeration it may be possible to maintain DO with a higher biomass and achieve greater productivity. Aerators are, however, often not available or feasible in rural regions where static pond culture is employed. Open systems Open system is the use of the environment as fish farm (e.g. cages), i.e. the culture organisms are confined or protected within the farm in a vast amount of water (e.g. a lake or an ocean) so that water quality is maintained by natural flows and processing. There is no artificial circulation of water through or within the system. Cage system classified as open systems when they are placed within a large body of water such as an ocean or an estuary. In these cage systems the fish are generally at high density and artificial feed is supplied. Water quality is, however, maintained by natural currents and tides. Therefore, these are intensive open systems. Open systems tend to have low operating costs, as there is no requirement for pumping. Capital costs vary greatly depending on the type of culture. Seasonal variation in environment result in large variation in growth rate and this is the most disadvantages of open system.
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